Conventional skin care products and other external preparations contain resin particles to fix skin flaws (to cover up spots, freckles, pores, etc.) by means of multiple light scattering effects and to improve spreading upon their application to the skin, as well as for various other purposes. Those resin particles are also blended with coating materials and light diffusion members to exploit multiple light scattering effects for matting or light diffusing purposes.
The external preparations containing the resin particles are in some cases required to have improved sweat and sebum absorbance so that they can render the skin smooth and silky when applied to the skin. Therefore, the resin particles used with the external preparations desirably have some water and oil absorbance.
For example, Patent Document 1, discloses a spherical polymer having an average particle diameter of 1 μm to 50 μm and an apparent specific gravity of 1.0 or less, each particle including one, two, or more spherical hollow tiny spaces inside it. The spherical polymer has some water and oil absorbance, absorbing 89.5 g to 110 g of water and 57.8 g to 82.3 g of oil (oleic acid) per every 100 g.
Patent Document 2 discloses porous spherical cellulose fine particles having an outer shell layer and a porous inner core having a porosity of 5% to 50%. The porous spherical cellulose fine particles have some water and oil absorbance, absorbing 170 g of water and 70 g of oil per every 100 g.
Patent Document 3 discloses porous spherical resin powder having particle diameters of 1 μm to 40 μm and an average particle diameter of 2 μm to 20 μm, the powder including pores of various sizes on the spherical surface with the mode pore diameter ranging from 5 angstroms to 160 angstroms (0.5 nm to 16 nm). The porous spherical resin powder has some water and oil absorbance, absorbing 74.6 g to 78.2 g of water and 81.4 g to 87.6 g of oil (oleic acid) per every 100 g.
Patent Document 4 discloses hollow flattened polymer fine particles having a shell wall made of an organic macromolecular compound. The hollow polymer fine particles become spherical upon absorbing a liquid substance and have some water and oil absorbance.